Rhacophytales

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Rhacophytales
Rhacophyton1.jpg
Rhacophyton sp.
Scientific classification
Kingdom:
Division:
Order:
Rhacophytales
Genera

Chlidanophyton
Ellesmeris
Eocladoxylon
Protocephalopteris
Protopteridophyton
Rhacophyton

Rhacophytales are an extinct group of plants from the Devonian period.

The representatives are characterized by a unique branching system in which bi- and quadriseriate units occur which are located in the axils of special structures, the aphlebiae. These are abnormal leaflets on the rhachis of ferns. The appendages of the last branching stage can be dichotomously branched, in some forms they stand in one plane. The vascular system consists of a clepsydroid primary xylem with a cross section and a secondary xylem. The sporangia are in groups and have no annulus. All representatives must have been homosporous.

The exact taxonomic position of Rhacophytales is still unclear. Rhacophyton was considered to be part of Aneurophytales (a progymnosperm order) in the past, when it was regarded as a precursor of seed ferns and true ferns. It was considered to be in Protopteridales, Zygopteridales, or the basal group in Coenopteridales, an polyphyletic group containing also Stauropteridales and Zygopteridales.

The representatives of the order share characteristics with some representatives of Iridopteridales and the progymnosperms. Some authors put them as a family in Zygopteridales, a fossil fern group. With them, they share glass-shaped xylem and quadriseriate branching. With the progymnosperms they share secondary xylem.

Taylor, Taylor and Krings (2009) see them as more evolved than Trimerophyta from which they originated, but they lack the organ differentiation found in the somewhat younger fern-like plants.

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<span class="mw-page-title-main">Lycopodiopsida</span> Class of vascular plants

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<span class="mw-page-title-main">Ginkgoales</span> Order of plants

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<span class="mw-page-title-main">Lycophyte</span> Broadly circumscribed group of spore bearing plants

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<i>Archaeopteris</i> Extinct genus of Devonian vascular plants

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<span class="mw-page-title-main">Progymnosperm</span> Extinct class of vascular plants

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Psilophyton is a genus of extinct vascular plants. Described in 1859, it was one of the first fossil plants to be found which was of Devonian age. Specimens have been found in northern Maine, USA; Gaspé Bay, Quebec and New Brunswick, Canada; the Czech Republic; and Yunnan, China. Plants lacked leaves or true roots; spore-forming organs or sporangia were borne on the ends of branched clusters. It is significantly more complex than some other plants of comparable age and is thought to be part of the group from within which the modern ferns and seed plants evolved.

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Polysporangiophytes, also called polysporangiates or formally Polysporangiophyta, are plants in which the spore-bearing generation (sporophyte) has branching stems (axes) that bear sporangia. The name literally means 'many sporangia plant'. The clade includes all land plants (embryophytes) except for the bryophytes whose sporophytes are normally unbranched, even if a few exceptional cases occur. While the definition is independent of the presence of vascular tissue, all living polysporangiophytes also have vascular tissue, i.e., are vascular plants or tracheophytes. Extinct polysporangiophytes are known that have no vascular tissue and so are not tracheophytes.

<span class="mw-page-title-main">Lepidodendrales</span> Extinct order of vascular tree-like plants

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<i>Pertica</i> Extinct genus of plants

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<span class="mw-page-title-main">Sphenophyllales</span> Order of plants

Sphenophyllales is an extinct order of articulate land plants and a sister group to the present-day Equisetales (horsetails). They are fossils dating from the Devonian to the Triassic. They were common during the Late Pennsylvanian to Early Permian, with most of the fossils coming from the Carboniferous period.

Psilophytopsida is a now obsolete class containing one order, Psilophytales, which was previously used to classify a number of extinct plants which are now placed elsewhere. The class was established in 1917, under the name Psilophyta, with only three genera for a group of fossil plants from the Upper Silurian and Devonian periods which lack true roots and leaves, but have a vascular system within a branching cylindrical stem. The living Psilotaceae, the whisk-ferns, were sometimes added to the class, which was then usually called Psilopsida. This classification is no longer in use.

<i>Tetraxylopteris</i> Extinct genus of vascular plants

Tetraxylopteris is a genus of extinct vascular plants of the Middle to Upper Devonian. Fossils were first found in New York State, USA. A second species was later found in Venezuela.

<i>Taeniocrada</i> Extinct genus of Devonian plants

Taeniocrada is a genus of extinct plants of Devonian age. It is used as a form genus for fossil plants with leafless flattened stems which divided dichotomously and had prominent midribs regarded as containing vascular tissues. It has been suggested that some species assigned to this genus were aquatic.

Rotafolia songziensis is a species of the extinct Sphenophyllales horsetails.

Calamopityaceae is the largest family of the division of extinct seed-bearing plants (spermatophytes) known as Pteridospermatophyta. It is the only family in the monotypic order Calamopityales. This family is characterized by its petioles and specific wood pattern, and it grew only in the Paleozoic era, specifically in North America and Europe. Three form genera within the family are diagnosed by their stem structure: Calamopitys, Stenomyelon, and Diichinia. It was named by Solms-Laubach in 1896. Since then, its genera have been added to and grouped differently.

The barinophytes are a group of extinct vascular plants (tracheophytes). Their relationship with other vascular plants is unclear. They have been treated as the separate class Barinophytopsida, the order Barinophytales of uncertain class and as a family or clade Barinophytaceae within the zosterophylls. They have also been considered to be possible lycopodiopsids.

References

Thomas N. Taylor, Edith L. Taylor, Michael Krings: Paleobotany. The Biology and Evolution of Fossil Plants . Second Edition, Academic Press 2009, ISBN   978-0-12-373972-8, p. 401-405.